1. Field of the Invention
The present invention relates to a method as well a device for preventing and/or extinguishing fires in enclosed spaces in which the internal air atmosphere is not permitted to exceed a predefined temperature value.
2. Description of the Related Art
An enclosed space where the internal air atmosphere may not exceed a predefined temperature, such as for example a cold storage, archive or IT area, is usually equipped with an air conditioning system in order to air condition the space accordingly. The air conditioning system is designed and correspondingly dimensioned such that a sufficient amount of heat, thermal energy respectively, can be discharged from the internal air atmosphere within the enclosed space so as to maintain the temperature inside the space within a predefined range. In the case of a cold storage area, for example, the temperature to be maintained is usually of a value which requires virtually permanent cooling and thus, the continuous operation of an air conditioning system, since temperature fluctuations are preferably also to be avoided in this case. This applies in particular to deep-freeze storage areas which are operated at temperatures to −20° C.
Air conditioning systems are however also utilized in IT rooms or switchgear cabinets, for example, in order to prevent—in particular due to the heat produced within the space by electronic components, etc.—the temperature of the internal air atmosphere within the space from reaching a critical value.
The air conditioning system is thereby to be dimensioned such that a sufficient amount of heat can be discharged from the internal air atmosphere within the space at any time so that the temperature within the space will not exceed the temperature predefined based on need and application.
The amount of heat to be discharged by the air conditioning system from the internal air atmosphere within the space is dependent on the flow of heat diffused through the inside shell of the space (heat conduction). Should heat-radiating objects be located in the enclosed space, the heat generated within the space adds to the further not insignificant amount of heat to be discharged to the outside. In particular in the case of areas housing servers, but also in the case of switchgear cabinets housing computer components, sufficiently discharging the heat which develops plays a crucial role in effectively preventing overheating and malfunction or even destruction of the electronic components.
As a fire prevention method for enclosed spaces which people only enter occasionally, for example, and in which the equipment therein reacts sensitively to the effects of water, it is known to address a risk of fire by lowering the oxygen concentration in the space's internal air atmosphere to a specific inertization level of e.g., 15% by volume or lower oxygen content on a sustained basis. Lowering the oxygen concentration—in comparison to the almost 21% by volume oxygen level of natural ambient air—considerably reduces the inflammability of most flammable materials.
The main area of application for this type of “inerting technology,” as the flooding of an area at risk of fire with oxygen-displacing gas such as carbon dioxide, nitrogen, noble gases or mixtures of these gases is called, are IT areas, electrical switchgear and distributor compartments, enclosed facilities as well as storage areas for high-value commodities.
However, employing the inerting technology in spaces in which the internal air atmosphere cannot exceed a predefined temperature value is coupled with certain problems. This is due to the fact that inert gas must be regularly or continually added to the internal air atmosphere of the space so as to maintain the inertization level set for the internal air atmosphere. Otherwise, depending on the space's air tightness and air change rate, the specifically-set oxygen concentration gradient between the internal air atmosphere of the enclosed space on the one hand and the external ambient air on the other would sooner or later be abolished.
Therefore, conventional systems which use inerting technology for fire prevention are usually equipped with a system to provide an oxygen-displacing (inert) gas. This system is thereby designed, subject to the oxygen content in the internal air atmosphere of the space, to feed a sufficient amount of inert gas into the space to maintain the inertization level. A nitrogen generator connected to an air compressor lends itself particularly well to a system for providing an inert gas, providing direct on-site generating of the inert gas as needed (here, i.e., the nitrogen-charged air). Such a nitrogen generator effects compression of the normal outside air in a compressor and separation into nitrogen-enriched air and residual gases with hollow fiber membranes. While the residual gases are discharged to the outside, the nitrogen-charged air replaces a portion of the atmospheric air in the enclosed space and thereby reduces the necessary oxygen percentage.
The supplying of the nitrogen-charged air is normally activated as soon as the oxygen concentration in the internal air atmosphere of the space exceeds a predefined threshold. The pre-defined threshold is set subject to the inertization level to be maintained.
Using such a system to prevent fires in spaces in which the internal atmospheric air may not exceed a predefined temperature is coupled with certain disadvantages since introducing thermal energy (heat) into the internal air atmosphere of the space is also unavoidable due to the regular or continual addition of inert gas. The air conditioning system then also needs to subsequently discharge this additionally-introduced thermal energy. Hence, the air conditioning system used must be of accordingly larger dimensioning. It is in particular to be ensured that the additional thermal energy resulting inside the space as a consequence of the continuous or regular adding of inert gas can also be effectively discharged again. It is thereby to be additionally considered that the nitrogen-charged air produced in a nitrogen generator and fed into the space is usually of an increased temperature compared to the temperature of the ambient outside air.
Even when a nitrogen generator is not used to provide inert gas, but instead gas bottles, etc., are used to store the inert gas in compressed state, it must be considered that additional thermal energy is often introduced into the internal air atmosphere of the space in this case as well. There is therefore likewise the risk that additional increases in temperature will occur which need to be accordingly compensated by the air conditioning system.
It can therefore, be established that the use of a conventional inerting system in enclosed spaces in which the internal air atmosphere may not exceed a predefined temperature value is coupled with increased operating costs since the air conditioning system needed to air condition the space must be of correspondingly larger dimensioning.